Yamaha 751033 CM500 Headset with Built-In Microphone Combining closed-ear, noise-reducing headphones with a sensitive, electret microphone, the CM500 creates the ideal choice for audience-interactive DJs or school music labs. Crafted with high-impact materials and an ultra-flexible headband, its solid construction withstands repetitive twisting and hard use found in music labs and on the dance floor. Optional bias supply included for use with audio devices that do not provide 15V phantom power (two AAA batteries required, not included) . Other features include: 96 dB/mW of sensitivity; Distortion <0.2%; 20 Hz-20 kHz of full-spectrum frequency response. Includes 9' cord with 1/8 plug and 1/4 adaptor.